This invention relates to devices for controlling the rotation of spools from which strip material is being withdrawn.
Two U.S. Pat. Nos. 3,899,383 and 3,944,457 both of which patents are also assigned to the assignee of this application, describe machines for applying parallel strips of stretchable reflex-reflective material to casings for bicycle tires such that when the tire casing is subsequently vulcanized the reflective strips provide reflective sidewalls for the tire.
Prior to the present invention, the supply of strip material for these machines was wound on flanged reels with each wrap of the strip material wound directly over the preceding wrap. The reel was then mounted on a device on the machine which permitted the reel to rotate freely while the strip material was withdrawn by operation of the machine, and which had a friction brake for braking rotation of the reel to prevent over-running of the reel and spilling of the strip material when strip material was no longer being withdrawn by the machine.
Such a reel held a rather short length of the strip material (i.e. about 330 feet), however, and thus required rather frequent changes during production runs.
Techniques have now been developed for level winding stretchable strip material on a core (e.g. in the manner thread is wound on a spool) so that each layer of strip material around the core consists of a plurality of adjacent wraps and each wrap crosses the wraps upon which it is wound. Such a spool can hold a much greater length of strip material (e.g. in the range of 4500 to 9000 feet) and thus requires much less frequent changing during production. The aforementioned devices for supporting reels are not suitable for use with such spools, however, because the level wound spools have so much inertia that tension in the strip material is not sufficient to start and maintain proper rotation of the spool without introducing excessive stretch into the strip material.